I answered before I checked this website. It was a computer voice that just said "goodbye". I thought it was funny. Now I know not to answer this call.
Thanks to everyone for posting!
You answered your own question about why they can't be stopped. Because they call from all different locations, and because the numbers they are calling from are fake. I can tell you for a fact that they are going to keep calling you because they're criminals trying to steal your money. People say the do not call list does not work. Yes it does work. Just think about how many more calls you would be getting from legal telemarketers if you weren't on the list. What the do not call list has also done for you is eliminate all the legal telemarketers thereby highlighting all the criminals and scammers for you.
What a PERFECT response to a person who posts complaints, and refuses to read multiple pages, that would have made the questions unnecessary. As you have said, the do not call registry works very well, but only with legitimate businesses. Call blocking can work, but informing others of the various scams, before they are victimized, will be more helpful, in the long run.
Finally, a voice of reason. I agree completely, if you are still getting calls after being listed on the DNC, assume that the caller is a criminal. If you don't want to be bothered get a call blocker; it won't stop them but it will slow them down. If you don't want to do that then just don't answer.